A fluid dispersion where a hardly water-soluble agrochemical active ingredient is dispersed in water can be applied to spraying and therefore the hardly water-soluble agrochemical active ingredient can spread widely by aerial spraying. In the case that a hardly water-soluble agrochemical active ingredient liquid, its aqueous dispersion may be prepared by diluting the liquid active ingredient with emulsifier such as surfactant. When it comes to a solid and hardly water-soluble agrochemical active ingredient, the solid active ingredient is liquefied by dissolving it in organic solvent and thereafter dissolving the liquefied active ingredient in water in the presence of a water-attracting surfactant, thereby obtaining an aqueous dispersion containing the agrochemical active ingredient. By such a method with assistance of a surfactant or water-soluble polymer and the like, aqueous dispersion of hardly water-soluble agrochemical active ingredients may be prepared, however, the obtained aqueous dispersion has problems associated with storage stability. The problems include a phase separation of the aqueous dispersion while being stored, flocculation of the agrochemical active ingredient, and segmentation of agglomerate of the agrochemical active ingredient.
JP H10-182302A (patent document 1) suggests an aqueous agrochemical composition having a formulation of emulsion or suspension, and comprising an agrochemical active ingredient, protein, polyvinyl alcohol (hereinafter, abbreviated as “PVA”), and surfactant. The patent document 1 also discloses the aqueous agrochemical composition exhibited excellent storing stability for a long term.
The patent document 1 describes that the PVA adopts an unmodified PVA having saponification degree of 90% or less (paragraph 0013), and the surfactant adopts non-ionic, cationic, anionic, or zwitterionic surfactant (paragraph 0015).
JP2002-293702A (patent document 2) discloses aqueous suspension formulation in which dispersoids does not agglomerate while stored, the aqueous suspension formulation being capable of spraying directly to paddy under submerged conditions without dilution. The aqueous suspension formulation is an aqueous suspension where a hardly water-soluble weeding active ingredient is dispersed in water medium in the presence of modified polyvinyl alcohol (modified PVA). As the modified PVA, PVA modified with alkyl group at the terminal thereof, PVA modified with alkyl group in side chain thereof, PVA modified with carboxyl group, PVA modified with cation, PVA modified with silicon-containing group, ethylene sulfonic acid-modified PVA, or PVA modified with acetoacetyl group may be used (paragraph 0011).
Moreover, JP2014-111244A (patent document 3) discloses a polymer-based surfactant utilizing a PVA containing polyoxyalkylene monomer unit. The patent document 3 also discloses the use of the surfactant including emulsifier for agrochemical emulsion or dispersing agent for agrochemical granule (paragraph 0072).
The patent document 3 discloses in example the follows: an aqueous solution using the surfactant had excellent bubble stability; and aqueous dispersion of calcium carbonate particles having an average diameter of 1 to 1.8 μm were stably kept for 30 days of more without separation of the dispersoid phase from water phase.
The paragraph 0021 in the patent document 3 explains that hydrophobic interaction between polyoxyalkylene groups would have been encouraged in polyoxyethylene modified PVA molecules, and thereby demonstrating excellent activity of the surfactant.